This invention relates to ethylenically unsaturated macromers prepared from allophanate-modified isocyanates which contain reactive unsaturation, pre-formed stabilizers prepared from these novel ethylenic unsaturated macromers, polymer polyols prepared from the macromers and the pre-formed stabilizers, and processes for the preparation of these compositions.
Allophanate-modified diphenylmethane diisocyanates and prepolymers thereof are known and described in, for example, U.S. Pat. Nos. 5,319,053, 5,319,054, 5,440,003, 5,663,272 and 5,686,042. U.S. Pat. No. 5,319,053 discloses a process for preparing stable liquid allophanate-modified MDI isocyanates and prepolymers of these allophanate-modified MDI isocyanates. This process comprises reacting a specific MDI isomer composition with an aliphatic alcohol containing between 1 and 36 carbon atoms to give an allophanate-modified MDI having an NCO group content of 12 to 32.5%.
Various allophanate-modified MDI's, prepolymers and other modifications thereof, and processes for their preparation, and which can be used in various end uses such as, for example, footwear and flexible foams, as is known and described in, for example, U.S. Pat. Nos. 5,567,793, 5,663,272, 5,686,042, 5,821,275, 5,874,485 and 6,271,279 and in EP 641,812.
A number of methods for inducing reactive unsaturation into a polyol, thereby forming a macromer, are known in the art. U.S. Pat. No. 6,013,731 teaches several techniques, including reaction of a polyol with unsaturated isocyanates (such as isocyanatoethylmethacrylate (IEM) or α,α-dimethyl metaisopropenyl benzylisocyanate (i.e. TMI)), or reaction of a polyol with maleic acid or maleic anhydride, followed by isomerization of the maleate bond to the more reactive fumarate bond. A macromer prepared by transesterification of a vinylalkoxy silane with a polyol has been disclosed in EP 0,162,589.
A pre-formed stabilizer is defined as an intermediate obtained by reacting a macromer containing reactive unsaturation (e.g. acrylate, methacrylate, maleate, etc.) with monomers (e.g. acrylonitrile, styrene, methyl methacrylate, etc.), optionally in a diluent or a solvent (e.g. methanol, isopropanol, toluene, ethylbenzene, polyether polyols, etc.) to give a co-polymer (dispersion having e.g. a low solids content (e.g. <20%), or soluble grafts, etc.).
A pre-formed stabilizer (PFS) is particularly useful for preparing a polymer polyol having a lower viscosity at a high solids content. In the pre-formed stabilizer processes, a macromer is reacted with monomers to form a co-polymer composed of macromer and monomers. These co-polymers comprising a macromer and monomers are commonly referred to as pre-formed stabilizers (PFS). Reaction conditions may be controlled such that a portion of the co-polymer precipitates from solution to form a solid. In many applications, a dispersion having a low solids content (e.g., 3 to 15% by weight) is obtained. Preferably, the reaction conditions are controlled such that the particle size is small, thereby enabling the particles to function as “seeds” in the polymer polyol reaction.
Pre-formed stabilizers of U.S. Pat. No. 5,196,476 are prepared by polymerizing a macromer and one or more ethylenically unsaturated monomers in the presence of a free-radical polymerization initiator and a liquid diluent in which the pre-formed stabilizer is essentially insoluble. EP 0,786,480 discloses a process for the preparation of a pre-formed stabilizer by polymerizing, in the presence of a free-radical initiator, from 5 to 40% by weight of one or more ethylenically unsaturated monomers in the presence of a liquid polyol comprising at least 30% by weight (based on the total weight of the polyol) of a coupled polyol which may contain induced unsaturation. These pre-formed stabilizers can be used to prepare polymer polyols which are stable and have a narrow particle size distribution. The coupled polyol is necessary to achieve a small particle size in the pre-formed stabilizer, which preferably ranges from 0.1 to 0.7 micron. U.S. Pat. Nos. 6,013,731 and 5,990,185 also disclose pre-formed stabilizer compositions comprising the reaction product of a polyol, a macromer, at least one ethylenically unsaturated monomer, and a free radical polymerization initiator.
Large, bulky molecules are known to be effective macromers because less material can be used to sterically stabilize the particles. See, for example, EP 0786480. Generally, this is due to the fact that a highly branched polymer has a considerably larger excluded volume than a linear molecule (such as, e.g., a monol), and therefore less of the branched polymer is required. U.S. Pat. No. 5,196,476 discloses that functionalities of 2 and higher, and preferably 3 and higher, are suitable to prepare macromers. EP 0,162,589 and U.S. Pat. No. 5,990,185 describe a macromer, and polymer polyols prepared therefrom, wherein the macromer is prepared by transesterification of a vinyl alkoxysilane with a polyol. Coupling multi-functional polyols with polyisocyanates is also known and described in the field of polymer polyols as a suitable means to increase the molecular weight of the macromer. EP 0786480 discloses a process for preparation of a pre-formed stabilizer wherein the liquid polyol comprises at least 30% coupled polyol. As described therein, a high concentration of coupled polyol is useful for obtaining particles with a small particle size in the pre-formed stabilizer (PFS) and the induction of reactive unsaturation into a coupled polyol is a useful means for incorporating coupled polyol into the particles. U.S. Pat. No. 6,013,731 describes enhancing the stability of the dispersion by coupling high molecular weight polyols to form an even higher molecular weight product. Macromers prepared from polyols with low intrinsic unsaturation (<0.020 meq/gram) are also described therein. This patent further discloses that such polyols have a low concentration of oxyalkylated, allylic unsaturation-containing monols, and are therefore advantageous because the high concentration of monols present in conventional polyols lowers the average functionality of the polyol.
Macromers based on multi-functional polyols and which have multiple sites of reactive unsaturation are described in U.S. Pat. No. 5,196,476. As described therein, there is an upper limit to the concentration of unsaturation when making macromers by the maleic anhydride route. If the ratio of moles of unsaturation per mole of polyol is too high, then there is a higher probability that species will be formed which have more than one double bond per molecule. Typically, the '476 patent employs from about 0.5 to about 1.5 moles, and preferably from about 0.7 to about 1.1 moles, of the reactive unsaturated compound for each mole of the alkoxylated polyol adduct.
U.S. Pat. No. 5,854,386 discloses stabilizers for polymer polyols which contain both hydroxyl-functionality and unsaturation-functionality. These are prepared by oxyalkylating an unsaturated monomer having at least one oxyalkylatable hydrogen in the presence of an effective amount of a DMC catalyst, and optionally, in the presence of a free-radial polymerization inhibitor. These stabilizers preferably correspond to mixtures containing one or more of the two formulae: R[—(—R2—O—)nH]o or R—(—X—{—(R2—O)n—H}m)o wherein: o is an integer between 1 and 8; n is an integer whose average value is such that the product n·o is from 10 to 500; R2 is alkylene or substituted alkylene; X is a linking group; and R is a C2-30 hydrocarbon containing at least one site of ethylenic or ethylynic (acetylenic) unsaturation, optionally substituted by non-reactive groups and optionally containing interspersed heteroatoms. R may be aliphatic, cycloaliphatic, aromatic, arylaliphatic, heteroaromatic, etc. with the proviso that when R is aromatic or heteroaromatic, the aromatic ring structure is substituted by at least one ethylenic or ethylynic radical-containing group.
There is a continuing need for novel macromers and novel preformed stabilizers to further advance the properties and characteristics of polymer polyols prepared from these macromers and preformed stabilizers. Although numerous macromers and preformed stabilizers are known, these have not previously been prepared from allophanate-modified diisocyanates which contain ethylenic unsaturation.